Roll gap gage control

ABSTRACT

A MILL HAVING A PLURALITY OF WORK ROLLS, SAID MILL HAVING HYDRAULIC SCREWDOWN MEANS AND POSITION CONTROL MEANS FOR SAID HYDRAULIC SCREWDOWN MEANS FOR CONTROLLING THE HYDRAULIC SCREWDOWN MEANS TO SET THE GAP BETWEEN SAID WORK ROLLS. IN PARTICULAR, THIS INVENTION PROVIDES A FIRST MEANS FOR DERIVING A FIRST SIGNAL INDICATIVE OF THE LOAD ON SAID WORK ROLLS, AND SECOND MEANS FOR COMBINING SAID FIRST SIGNAL WITH A SECOND SIGNAL FROM SAID POSITION CONTROL   MEANS TO DERIVE AN ERROR SIGNAL TO EFFECT CONSTANT ROLL GAP CONTROL BY CONTROLLING THE HYDRAULIC SCREWDOWN MEANS.

A 7 T. RASTELLI 3,559,432

ROLL GAP GAGE CQNTROL med May 29, 1968 r s Sheets-Sheet 1 INVENT OR TdesQave Ras+e\\\ BY mao WWW ATTORNEYS 1'. RASTELLI ROLL GAP GAGE CONTROL Fax-2'; 1971 5 Sheets$heet 3 Filed May 29, 1968 L INVENTOR Te\es-For-c. RQs re\ 112% A W M 1 ZfiZNEYS Feb. 2, 1971 4 T.RA$TELLl- 3,559,432

ROLL GAP GAGE' CONTROL Filed May 29, 1968 5 Sheets-Sheet 4 PULSE SOURCE 7 INVENTOR fewsFovs Rxs-K-eflh :mzwwm Feb. 2, 1971 'r. RASTELLI 3,559,432

ROLL GAP GAGE CONTROL Filed May.29, 1968 5 Sheets-Sheet 5 PRESSURE REGULHTOR 5 WHY SERVO VHL 80 OPEN VFILVE REULHTOK 5 WHY MECHHNICQL FEEDBHCK SERVO VHLVE FEEDBHCH INVENTOR Kass-(ova Woks-Ham United States Patent 3,559,432 ROLL GAP GAGE CONTROL Telesfore Rastelli, Cheshire, Conn., assignor to Textron,

Inc., Providence, R.I., a corporation of Delaware Filed May 29, 1968, Ser. No. 732,998 Int. Cl. B21b 37/08 US. CI. 7219 13 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a system for controlling the gap between rolls of a mill and, more particularly, to a system for deriving a signal to effect constant roll gap control.

In a mill such as used for rolling metals and the like, which incorporates position control hydraulic screwdown means, it is highly desirable that means he provided to effect the continuous control of the roll gap. It is important that this be accomplished without affecting the use of the hydraulic screwdown adjustment for initial mill setting and for resetting for long-range drift.

Accordingly, this invention provides a new and improved apparatus and system for effecting constant roll gap gage control. With the use of this invention, a stiff mill or a soft mill can be obtained. A soft mill can be made by mill adjustment in the direction of mill deflection, whereas a stiff mill is accomplished by a mill adjustment in the opposite direction of mill deflection.

This invention provides advantages over the prior art in that there are no gears 'or screws in the chocks which must be duplicated for spare chocks for roll changing. In addition, there are no screwdown drives which must be disconnected when changing rolls. Furthermore, with this invention, the mill screwdown position may be set prior to entering the strip into the mill and the mill loads are not in excess of rolling loads. This equipment also achieves significant cost advantages by reducing the number of sensors required.

In accordance with this invention, gage control is effected by the use of an error signal which indicates that a mill adjustment must be made. The error signal is derived from a screwdown transducer and a load cell. The signals from these devices are so related that their combination will produce an error signal indicative of the change in roll gap from the desired setting. The error signal so derived is directed to a servo valve to command a mill adjustment in a direction to correct the error. In a soft mill, the error signal is used to command a mill adjustment in a direction which will reduce the change in mill load.

In view of the foregoing, it is an object of this invention to provide a new and improved roll gap control system.

Another object of this invention is to provide a new and improved roll gap control system which, by adjustment, may provide either a stiff or soft mill.

Still other objects and advantages of this invention will in part be obvious and will in part be apparent from the specification.

3,559,432 Patented Feb. 2, 1971 The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the constructions hereinafter set forth and the scope of the invention will be indicated in the claims.

For a fuller understanding of the invention, reference is had to"the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 diagrammatically illustrates the mill according to this invention;

FIG. 2 is a block diagram illustrating the hydraulics and a portion of the electrical system for controlling the mill according to the invention;

FIG. 3 is a circuit diagram illustrating the electronic controls of the mill according to the invention;

FIG. 4 diagrammatically illustrates a modification according to this invention;

FIG. 5 is a diagrammatic illustration of another mill (only half being shown) having position control, according to the invention; and

FIG. 6 is a diagrammatic illustration of a three-way mechanical feedback servo valve for use in the embodiment of FIG. 5.

Referring to FIGS. 1 and 2, there is shown the mill housing at 10 in which a pair of work rolls 11 and 12 is supported. The work rolls in turn are supported, respectively, by back-up rolls 13 and 14, roll 14 being supported in a bearing chock 15 and roll 13 being supported in a bearing chock 16. The bearing chock 16 is movable within the housing 10 in a direction shown by the arrows in FIG. 1. A strip of material is shown being processed by the mill at 17.

In order to set the mill stiffness, a hydraulic cylinder 20 is provided having a piston 21, the lower member 22 and an upper member 23. In the preferred embodiment, the lower member 22 pushes downwardly on a load cell 24 to apply pressure to the bearing chock 16 to set the gap between the rolls 11 and 12. The load cell 24 may be of the type sold by The Revere Corporation of America, Wallingford, Conn. A description of the operation of the load cell will be given in conjunction with the description of FIG. 3. Fluid is provided to the hydraulic cylinder 20 by means of passages 25 and 26, shown in FIG. 1.

In order to adjust the mill setting, there is provided a mechanism 28 controlling a screw 29 which controls the setting of a coil 30 forming a part of a displacement transducer, such as Model 24 DCDT-1000 sold by Sanborn Division of Hewlett Packard Corporation, Waltham, Mass. A core of the displacement transducer is shown at 31 and is mounted on a member 32 supported on the upper member 23 coupled to the piston 21. In this manner, the core 31 moves in accordance with the movement of the piston 21. Although there has been shown only one side of a mill, FIG. 1, it should be understood that the means for adjusting the roll gap also includes an adjusting screw drive means and clutch or coupling means for controlling the other side of the mill.

Referring now particularly to FIG. 1, there is shown the hydraulics and a portion of the electrical circuit for controlling the mill, according to the invention. In order to derive the error signal, signals are provided form the load cell which indicates the upward force on the Work roll 11 and from the displacement transducer coil 30' as a result of the position of the core 31. These two signals are then combined in the control circuitry shown at 35 to produce an error signal which then controls a servo valve 36 which, in turn, controls the amount and direction of fluid entering the hydraulic cylinder 20. The fluid is obtained from a hydraulic pump, sump and motor arrangement generally shown at 37. As will be noted in FIG. 2, signals are also obtained from a rear transducer over a dotted line 38 and from a rear load cell over dotted line 39 and are then separately analyzed by a control system shown at 40 to provide an error signal on line 41, which then operates to control a servo valve 42. Fluid is provided through the valve 42 to the hydraulic cylinder controlling the other side or rear of the mill by way of a pump, sump and motor arrangement generaly shown at 43.

Referring now to FIG. 3, the electrical control circuit is shown according to this invention. The load cell is generally shown at 24 and includes a bridge network 45 for deriving a signal which is applied to a bridge balancing network 46, thence to pre-amplifier 47. The amplifier may be of the type produced by Nexus Research Laboratories of Canton, Mass., Catalog No. CDA 22. Thereafter, the signal from the load cell is applied to a mill stiffness control circiut 48 which comprises two variable resistors 49 and 50 for controlling the range of operation. Thereafter, a signal is derived from a center tapped potentiometer 51 and is applied to a servo valve amplifier 55. The amplifier 55 may be of the type sold by Nashua Servo Controls Company, Nashua, NH, Model 720. At the same time, a signal is applied from the displacement transducer coil 30 to the amplifier 55. The output of the amplifier 55 which is a function of the two signals, is then applied to the servo valve 36 through its coil 57 to control the passage of fluid into the hydraulic cylinder 20 to constantly control the gap betwen the work rolls 11 and 12. By the use of the center tapped resistor potentiometer 51, it is possible to apply either positive or negative feedback signals. By applying positive feedback signals, a stiff mill may be obtained and by applying negative feedback signals, a soft mill may be obtained.

It should also be understood that, in place of the load cell, pressure transducers may be used to measure the pressure of the hydraulic fluid within the cylinder 20. In addition, a sensor or sensing device may be built into the member 22 to measure piston rod strain or into the housing 10 in order to determine the load. Accordingly, it is desired that the invention not be limited to the particular use of the load cell shown. It should be further understood that this invention is also applicable to a two-high mill and other mill configurations.

With reference now to FIG. 4, there is shown a modification of the invention. In this construction, two rolls 60 and 61 are supported in a housing such that their journals are mounted one on top of the other. In order to locate one roll with respect to the other, a double-acting hydraulic cylinder 62 is provided to which fluid is provided through a servo valve 63 controlled by electronic signals from an electronic amplifier 64. The pressure on the rolls is detected by the use of a load cell 65 which provides a signal, which signal is combined with a signal provided from a displacement transducer 67. The outer coil 68 of transducer 67 is controlled with respect to the inner core 60 by a stepper motor 70 which controls a lead screw 71 to set the position of the coil 68. The motor 70 is responsive to signals from a pulse signal source 72.

Now referring to FIG. 5, there is shown a roll gage control system which utilizes a three-way servo valve in combination with feedback means to effect mill adjustment. In this figure, a half of a mill is shown generally at and includes a plurality of rolls 81 adapted to roll material passing between the work rolls. To effect mill position control, there is provided a double-acting hydraulic cylinder 82 having a piston 83 and piston rods 84. The rods 84 act through an intermediate member to force the roll journals, supporting the rolls and, thus the rolls, together. The cylinder 82 has two chambers, one being the upper shown at 85 and the lower chamber shown at 86. Fluid is provided to control the piston 83 by way of a source or supply generally shown at 87 through the tube 88. Fluid to the upper chamber 85 is provided through a tubing 89 positioned on one side of a flow divider shown at 90. The pressure in the upper chamber 85 is maintained constant by the use of an adjustable setting pressure regulator 91. In order to control the position of the rolls of the mill, tubes 93 and 94 are positioned on either side of the flow divider (so named in the drawing) for providing fluid through a three-way servo valve 95 which, essentially, is a two-position valve having a springpositioned spool. The servo valve 95 is electromagnetically controlled by signals provided from an amplifier 96 from signals provided from a transducer 97 having a coil 98 and a core 99 movable with the piston 83 and mounted on the rod 84. In operation, the position of the core 99 is adjusted by a motor 100 through a gear arrangement shown at 101 which moves a member 102 to position the coil 98 with respect to the core 99. Also in operation, the amplifier 96 provides a signal to the electromagnet of the valve 95 to permit fluid to flow through the tube 93 into the lower chamber 86. When there is no signal sulficient to cause the electromagnet to move the spool of the valve 95, fluid will flow through the tubing 94 into the lower chamber 86. As may be noted, there is provided a pressure regulator 103 coupled to the tubing 94. The regulator 103 acts to cause the pressure in the lower chamber 86 to drop to the preset back pressure, set by the regulator 103. The servo valve 95 is connected such that the tubing 94 is coupled to the lower chamber 86.

FIG. 6 of the drawings shows a modification of the device of FIG. 5, in that, in place of the electrical feedback system and the three-way electrical servo valve, a three-way mechanical servo valve is used. The valve 110 is controlled by a feedback rack arrangement 111 which controls the position of the spool of the valve 110.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description are efficiently attained and since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It should also be understood that the following claims are intended to cover all the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. In a mill having a plurality of work rolls and at least one back-up roll for each work roll, said mill having hydraulic screwdown means in the form of a cylinder including a piston and piston rod adapted to act on at least one of said back-up rolls, position control means for said hydraulic screwdown means for controlling the hydraulic screwdown means to position the back-up roll to set the gap between said work rolls, the improvement comprising first pressure responsive means for deriving a first signal indicative of the load on said work rolls, means for deriving a second signal indicative of the relative position of the rolls, means for combining the first signal with the second signal to derive an error signal, means for applying said error signal to said position control means to control said hydraulic screwdown means and effect constant roll gap control.

2. The arrangement of claim 1, further including a chock for supporting one of said back-up rolls, and a load cell included in said pressure responsive means for driving a first signal and positioned between said piston and said chock.

3. The arrangement of claim 2, wherein said position control means includes a displacement transducer comprising a coil body and a core movable with said piston within said coil body.

4. The arrangement of claim 3, including means for adjusting the position of the coil body.

5. The arrangement of claim 4, wherein said first means includes means for setting the stiffness of the mill to provide either a stiff or soft mill.

6. The arrangement of claim 2, wherein said position control means includes a stepping motor, a movable coil and a core, said stepping motor coupled to position said coil with respect to said core.

7. In a screwdown system for a mill having a plurality of rolls supported by roll supporting means, the improvement comprising in combination a double-acting hydraulic cylinder having upper and lower fluid chambers positioned on either side of a piston having rod means for causing said rolls to be forced together, first means for providing fluid to each of said chambers, second means for controlling the pressure of the fluid in said upper chamber, third means for controlling the flow of fluid into said lower chamber, said third means including roll position signal generating means responsive to the position of said piston and a servo valve responsive to a signal from said position signal generating means to control the fluid provided to the lower chamber of said cylinder.

8. The arrangement of claim 7, in which said means for deriving a second signal provides a position feedback signal and said position control means comprises a threeway servo valve responsive to said error signal to control the fluid provided to said lower chamber,

9. The arrangement of claim 8, including means operative to set the minimum back pressure of fluid in said lower chamber.

10. The arrangement of claim 8, wherein said position feedback means comprises a coil and core movable relative to each other.

11. The arrangement of claim 8, wherein said feedback means comprises a rack arrangement.

12. In a mill for rolling material between a pair of work rolls having back-up means for said rolls, said mill having screwdown means for controlling the gap between the work rolls, the improvement comprising said screwdown means is a double-acting hydraulic cylinder having upper and lower fluid chambers positioned on either side of a piston having rod means for causing said rolls to be forced together, first means for providing fluid to each of said chambers, second means for controlling the flow of fluid into said chamber, said second means including a roll position signal generating means responsive to the position of said piston and an electrically actuated servo valve responsive to a signal from said position signal generating means for controlling the fluid provided to the chamber of said cylinder,

13. The arrangement of claim 12 further comprising a member responsive to the pressure between said piston and said rolls for providing a signal indicative of the mill deflection as a result of rolling material, and means for combining said mill deflection signal and the signal from said position signal generating means to provide a command signal to said servo valve.

References Cited UNITED STATES PATENTS 3,128,630 4/1964 Briggs 73-432 3,178,919 4/1965 Varner 72--9 3,208,251 9/1965 Hulls et al. 72--l6X 3,285,049 11/ 1966 Neumann 72246 3,389,588 6/ 1968 Reinhardt et a1. 728 3,427,839 2/ 1969 Neumann 7220 3,431,762 3/1969 OBrien 7219 MILTON S. MEHR, Primary Examiner US. Cl. X.R. 

